Electrical interconnection boards, typically referred to as printed circuit, printed wiring or panel boards, normally have mounted onto them a plurality of electronic components such as dual-in-line ("DIP") electronic packages, which may be integrated circuit packages, or other types of electronic components formed with any number of leads. In some known devices, leads of electronic components are inserted into plated-through holes in the boards, which holes are electrically connected to various printed circuit paths on one or both sides of the board. Leads from the electronic devices would be individually soldered or collectively wave soldered so that the hole was filled with solder to permanently mount the component to the board and to make positive electrical interconnection with the printed circuit paths.
It is often desired to use the concept of plugability, that is, to be able to plug the leads of a component into a board for whatever purposes are desired and then to remove it if necessary. Such plugability is not possible with the method discussed above because the component leads are soldered to the printed circuit board. It is well-known, however, to provide a lead socket assembly in which one end is a lead receiving socket and the other end normally provides a solder tail or wire wrapping pin. See, for example, U.S. Pat. Nos. 4,186,990 and 4,296,549, assigned to the same assignee as named herein. The solder tail and wire wrapping pins project for some appreciable distance beyond the non-component side of the board and the lead receiving socket end normally projects a short distance beyond the other side of the board. The lead socket end is necessarily somewhat larger than might otherwise be desired because of the requirement that there be a tapered opening to facilitate inserting component leads and that there be an element within the socket assembly itself to frictionally engage the inserted component lead.
Prior known lead socket assemblies have been manufactured either by being machined or being stamped and formed. Machined socket assemblies have had certain deficiencies due to the fact that converging fingers of the lead socket contact are normally curved in a lateral direction with respect to their length, creating an inherent beam effect in the fingers which cause stresses to occur primarily at the point where the individual fingers are bent toward one another. That is, because of this beam configuration, the fingers are relatively stiff, so that flexing occurs primarily at the bending point rather than being distributed throughout the length of the fingers when a lead is inserted between them. In addition, because of the relative stiffness of the fingers, electrical component lead insertion and removal forces tend to be inconsistent from insert to insert over a period of time. Machined socket contacts also tend to be somewhat expensive. As examples of machined contacts, see U.S. Pat. Nos. 4,175,810 and 4,097,101, assigned to the same assignee as named herein.
Previous known lead socket assemblies which have also been stamped and formed out of strip metal have also faced certain disadvantages. These lead socket assemblies have been made of a single metal chosen to obtain a desired compromise as to strength, resiliency, cost and conductivity, depending on the particular characteristics preferred for the specific lead socket assembly. For example, where strength is considered to be a highly desired characteristic, the lead sockets have been made of a stronger material, thus trading off on other characteristics such as resiliency or cost. In addition, stamped and formed lead socket assemblies have not been preferred because it has been difficult to make stamped sockets perfectly round. Rather, they are substantially always somewhat egg-shaped, resulting in variable lead insertion and removal forces, and variability in physical and electrical contact.
While the prior art lead socket devices serve useful functions, their limitations have prevented their universal use where they otherwise might be the appropriate structure for various applications. Lead sockets therefore must preferably be capable of quickly and easily connecting and disconnecting with the leads of an electrical component without undue force. Each lead socket should also be able to provide excellent electrical conductivity and be capable of repeated connection and disconnection without damage or significant deterioration.